THE justly renowned documentaries in the “Up” series, of which “49 Up” is the seventh entry spread over 42 years, were supposed to be about class. They turned out to be about marriage.

In 1964, a group of TV filmmakers including Michael Apted, now the narrator-director of the series, asked an economically diverse group of British kids about who they were and who they thought they’d turn out to be.

Dropping by on the same people every seven years like an old friend – or an unwelcome relative – Apted has constructed a peerless, suspenseful work that develops character to a depth that would make Tolstoy jealous. If you have any interest in documentaries, watch the DVD of the first film, “7 Up” (“49 Up” hits DVD Nov. 14). You won’t be able to stop.

The series began with a vaguely leftist assumption that class is destiny. But every personal arc tells a conservative parable: Individual character matters, marriage and hard work create happiness, welfare the opposite. Take Jackie, a Cockney who broke off contact with the father of her first child, had two more, and remains single. She lives entirely on the dole and reveals herself to be bitter and frustrated.

One of the most compelling figures is Suzy, who grew up in cosseted splendor. At 21, after her parents’ divorce, she was brittle and depressed, having dropped her education and replaced it with chain smoking. She was disgusted with the idea of marriage and babies, but after she became a housewife her transformation was amazing. Now a matron of 49, she is utterly at peace.

The strangest case is Neil, a bright lad who by 28 was homeless and wandering the Shetland Islands in a lonesome funk. Now that he’s 49, though, he’s really hit bottom: He’s a government official.